At various stages of a typical paper making operation a moving, continuous sheet of paper is passed, at high speed, over a plurality of rolls which are rotated with respect to one another. For example, at one stage of the paper making operation the moving paper sheet is passed over a plurality of dryer rolls. Adjacent pairs of dryer rolls are rotated in opposite directions so that the paper is drawn from roll to roll. The roll surfaces are heated to evaporate moisture from the paper. The pressure applied to the moving paper sheet by pressing it against the roll faces also assists in moisture removal. At a subsequent stage of the paper making operation the moving paper sheet is typically passed between adjacent pairs of counter-rotating calender rolls (the "calender stack") which calender the paper by imparting the desired smooth finish thereto, after which the sheet is passed to a reel and onto a wind-up spool.
Since it is difficult to thread a full width moving paper sheet between a pair of counter-rotating rolls, a narrow tail is typically cut to one side of the moving sheet before the paper encounters the counterrotating rolls. The tail can be more easily threaded through the rolls and, once correctly threaded, is used to draw the full width of the paper sheet between the rolls. This method is used to transfer the paper from the last dryer roll through the calender stack, and is also used to transfer the paper from the calender stack to the reel and wind-up spool.
In the prior art, the paper tail threading procedure is typically time consuming and labour intensive. Often, the operating speed of most of the paper making machinery must be reduced so that the paper can be manually handled and guided between adjacent pairs of counter-rotating rolls. Conventionally, workmen use air hoses to direct blasts of air at the paper tail in an effort to force it into the desired position between a pair of in-running rolls, until the tail is caught and pulled through; after which the air hose must be used to direct the paper tail to the next pair of rolls in the sequence. Sometimes, mechanical prods, or hand-held dual rolls are used to force the tail into the desired position between the rolls. Unfortunately, these techniques are not only cumbersome and time-consuming, but also expose the workmen to possible serious injuries if their hands or arms become trapped between the rapidly rotating rolls.
The present invention provides a paper tail nip threader or "guide" for automatically guiding a moving paper tail from point to point within an operating paper machine; for example, over or around a contoured surface such as the surface of a roll. A plurality of such guides may be arranged to guide a moving paper tail at high speed over and between adjacent pairs of counter-rotating rolls, thereby vastly simplifying the tail handling and threading procedure and overcoming the foregoing difficulties by reducing labour costs, while operating the paper making machinery at its maximum speed and minimizing the potential for operator injuries.